And when you go to a store, they do not even list that (- or +) anymore, and maybe a DVD-RAM would be different, but anyway, all DVD-R or DVD-RW would be the same anymore.
But the DVD unit in the computer would be more flexible to handle all of it (includes DVD-RAM) whereas most DVD-RW in a computer nowadays handle the usual DVDs made.
The laptop I think if I remember handles all of those kind including the DVD-RAM, the newer or other computer may not handle the DVD-RAM, but I fail to see where they are even listed when going to a store anymore.
If you want DVD-RW just pick up DVD-RW, and if you want DVD-R then just pick those up, and make the DVD compatible to be read in all DVD drives.
Standard, standard, standard.
All have been combined probably, but DVD-RAM may still be a question, and no doubt, probably no one uses them anymore if they ever did in the first place.